Electronic computer equipment generally requires regulated power supplies that protect against non-uniform utility or line power. Often, critical loads such as computers require uninterrupted power supplies.
A current state-of-the art "front end" computer power system is shown in FIG. 1, comprising an AC/DC input power conditioning function shown in block 50, a DC bus 40, and one or more DC/DC converters/regulators 30. A rectifier/voltage doubler 10 converts utility power 5 (one-phase or three-phase AC) into high voltage DC (160-425 VDC). An energy storage/ripple filter 20 provides limited protection against power sags and further filters any AC component on the high voltage DC bus 40. A shunt capacitor (not shown) forms a simple implementation of such an energy storage/ripple filter circuit.
Such an implementation creates a system that draws energy from the utility only when the AC input voltage 5 rises above the filtered DC output voltage 40. Thus, large spikes of current are drawn from the utility. These large current spikes result in a higher than required volt-ampere product. The high volt-ampere product causes a low power factor ("P.F."). Power factor is given in terms of watts/(volts.times.amperes). A low power factor is considered undesirable by the utility, and often customers are surcharged when their power factor drops below a certain level.
The current spikes also cause harmonic distortion on the utility input 5. Many countries are imposing strict limitations on the amount of harmonic distortion that may be placed on the utility. Implementation of the energy storage/ripple filter 20 with a series inductor and shunt capacitor (not shown) offers improved power factor correction and reduced harmonic distortion at the expense of output voltage and energy lost through heat. For high power requirements, these components may be bulky, heavy and require special cooling systems.
A DC/DC converter/regulator 30 converts the unregulated high voltage (typically 160-425 VDC) DC on bus 40 into a highly regulated voltage suitable to power sensitive electronic components such as those used in computer logic circuits. This voltage (typically 5 VDC or less), isolated, regulated, and current-limited, is applied to low voltage bus 35. Blocks 30' and 30" represent other converters that may be attached to the high voltage DC bus 40.
Particularly for applications involving computer memory systems, the power supply of FIG. 1 may be further adapted. For example, FIG. 2 illustrates an addition to the system of FIG. 1 of a battery subsystem 60 to allow the supply of energy to a memory system when a power sag or outage occurs. The AC/DC input conditioner 50 is equivalent to blocks 10 and 20 in FIG. 1. Diode 70 is placed in series with the voltage bus 40 and a memory regulator system 90. The memory regulator 90 provides power to the computer's memory system.
The battery subsystem 60 provides the appropriate DC voltage during utility voltage sags or outages. This "battery back-up" voltage is connected to the high voltage DC bus 40 through diode 80. The battery subsystem 60 is comprised of a battery charger 61, a battery 62 (typically 48 or 96 VDC), and a DC/DC boost converter 63 (typically to approximately 160 VDC).
The system as illustrated in FIG. 2 does not maintain power to the entire computer during utility power sags or outages, but only to the memory or a portion of the memory. Although power is maintained to the memory system to maintain the current status of data processing, the computer operator experiences the loss of his/her computer resources. This condition is unacceptable in many computer environments.
If the computing environment requires non-interruption during power sags or outages, an "uninterruptible" power supply ("U.P.S.") must be added. FIG. 3 illustrates the use of such a system. The U.P.S. 100 is placed in series with the utility 5 and the computer or any critical load 120. The U.P.S. maintains AC voltage to the load whenever the utility power sags or experiences an outage. FIG. 4 is a block diagram of a typical U.P.S. The rectification block 130, which may include a three-phase bridge or a single-phase voltage doubler, provides an unregulated DC voltage to bus 140 in much the same way as 10 in FIG. 1. Energy storage and filtering is provided by block 170 (which may be an energy storage device such as a capacitor) in a manner similar to 20 in FIG. 1. The DC/AC inverter 180 converts the DC voltage on bus 140 to an AC voltage capable of powering a computer or other critical load, typically domestic 120 VAC at 60 Hz or European 240 VAC at 50 Hz. Current technology, especially for those systems working in a three-phase environment, uses a power switch 181 to excite a transformer 182 (which also functions as an isolation transformer) to create the AC output voltage. A harmonic filter 190 filters the output voltage to prevent high frequency harmonic components from leaving the system. The battery stack 160 provides DC voltage (typically approximately 400 VDC) through diode 220 to bus 140 whenever a utility power sag or outage occurs. A charger 150 provides a means for restoring energy to the battery stack 160.
A state-of-the art U.P.S. may provide 20 KVA output, enough to run a number of mini- or mainframe computers, or an entire computer room or office environment. This is achieved in the configuration shown in FIG. 4 by directing nearly 20 KW of power in one path through components designed to handle such power, such as very large capacitors and inductors. The isolation transformer 182 in such a U.P.S. may weigh well over one hundred pounds. Although the batteries 160 may be stored separately in a second refrigerator-size cabinet from the other components, and some of the components, such as the rectifier 130, the power switch 181, and the bypass/static switch 200 may be removable for repair, the large capacitors and inductors are not easily accessed and may remain hazardous even when the U.P.S. is taken off-line. Moreover, the state-of-the art U.P.S. is not fault-tolerant: if the power switch 181 fails, the U.P.S. must be taken off-line; if a battery in the stack 160 fails, the U.P.S. may not provide back-up power when needed.
The current use of a U.P.S. 100 to power a computer 120 or similar piece of equipment (FIG. 3) results in needless redundancy, as apparent from FIG. 5, in which the typical state-of-the art U.P.S. illustrated in FIG. 4 is simplified in block 100, and the typical computer "front end" power supply illustrated in FIG. 1 is simplified in block 120. As readily seen, because utility AC is converted to DC at 230, reconverted to AC at 250, and reconverted to DC at 300, not only are the latter two stages redundant, but the AC output stage 260 and AC input stage 290 are also redundant.
The current state-of-the art requires each power supply problem (regulation, "uninterruptibility," power level, input phases, line voltage, etc.) to be addressed with a unique hardware set. This approach is inefficient, costly, redundant and difficult for users to implement.